下稳定板形式对兴康特大桥颤振性能的影响

Effects of lower stabilizing plate forms on flutter performance of Xingkangte bridge

雅康高速泸定大渡河兴康特大桥跨越干热河谷区深大峡谷,其桥面中央设置了竖向稳定板以提高结构在复杂风环境下的颤振稳定性。对于钢桁加劲梁而言,下稳定板的布置形式具有一定的可变性,为了进一步优化下稳定板的抑振效果,研究了不同形式的下稳定板对该桥颤振性能的影响。首先,通过风洞试验测试了不同位置的单稳定板及不同形式的分离式稳定板对颤振临界风速的影响。然后,建立简化的二维CFD模型,通过气动力输入能量的大小及流场的变化规律对相应的气动机理进行了解释。研究结果表明:设置稳定板后,各个攻角下的颤振临界风速均得到不同的提高,尤其是在负攻角下。当负攻角的绝对值较大时,扭转运动的不稳定性成为了颤振发生的主要原因,稳定板通过阻碍漩涡移动、改变漩涡大小和增大迎风侧桥面板下侧负压区强度的方式提高扭转稳定性,因此,将中央稳定板设置为分离式竖向稳定板的效果更好。

For the expressway connecting Ya’an and Kangding,Xingkangte Bridge over Dadu River at Luding crosses the deep Grand Canyon in dry-hot valley area.Vertical stabilizing plates are installed on the center of the bridge deck to improve the structural flutter stability under complex wind environment.For steel truss stiffened girders,layout form of lower stabilizing plates has a certain variability.Here,in order to further optimize vibration suppression effect of lower stabilizing plates,effects of different forms of lower stabilizing plate on flutter performance of the bridge was studied.Firstly,effects of a single stabilizing plate at different locations and separating type stabilizing plates with different forms on critical flutter wind speed were tested in wind tunnel tests.Then simplified 2-D CFD models were established and the corresponding aerodynamic mechanism was explained with aerodynamic input energy values and varying laws of flow field.Study results showed that after installing stabilizing plates,critical flutter wind speeds at different attack angles increase,especially,in cases of negative attack angles;when the absolute value of negative attack angle is larger,the instability of torsional motion becomes the main cause of flutter,stabilizing plates improve torsional stability through blocking vortex movement,changing vortex size and increasing strength of negative pressure area under the windward side of the bridge deck,so it is better to set the central stabilizing plate as a separating type vertical stabilizing plate.